1,394 research outputs found
Anti-Zeno Effect for Quantum Transport in Disordered Systems
We demonstrate that repeated measurements in disordered systems can induce
quantum anti-Zeno effect under certain condition to enhance quantum transport.
The enhancement of energy transfer is really exhibited with a simple model
under repeated measurements. The optimal measurement interval for the anti-Zeno
effect and the maximal efficiency of energy transfer are specified in terms of
the relevant physical parameters. Since the environment acts as frequent
measurements on the system, the decoherence-induced energy transfer, which has
been discussed recently for photosynthetic complexes, may be interpreted in
terms of the anti-Zeno effect. We further find an interesting phenomenon, where
local decoherence or repeated measurements may even promote entanglement
generation between the non-local sites.Comment: 5pages, 3 figures; v2: published versio
Cluster-based architecture for fault-tolerant quantum computation
We present a detailed description of an architecture for fault-tolerant
quantum computation, which is based on the cluster model of encoded qubits. In
this cluster-based architecture, concatenated computation is implemented in a
quite different way from the usual circuit-based architecture where physical
gates are recursively replaced by logical gates with error-correction gadgets.
Instead, some relevant cluster states, say fundamental clusters, are
recursively constructed through verification and postselection in advance for
the higher-level one-way computation, which namely provides error-precorrection
of gate operations. A suitable code such as the Steane seven-qubit code is
adopted for transversal operations. This concatenated construction of verified
fundamental clusters has a simple transversal structure of logical errors, and
achieves a high noise threshold ~ 3 % for computation by using appropriate
verification procedures. Since the postselection is localized within each
fundamental cluster with the help of deterministic bare controlled-Z gates
without verification, divergence of resources is restrained, which reconciles
postselection with scalability.Comment: 16 pages, 34 figure
Successive phase transitions at finite temperatures of the supersolid in the three-dimensional extended Bose-Hubbard model
We study the finite temperature properties of the extended Bose-Hubbard model
on a cubic lattice. This model exhibits the so-called supersolid state. To
start with, we investigate ordering processes by quantum Monte Carlo
simulations, and find successive superfluid and solid phase transitions. There,
we find that the two order parameters compete with each other. We obtain the
finite temperature phase diagram, which contains the superfluid, the solid, the
supersolid and the disordered phase. We develop a mean-field theory to analyze
the ordering processes and compare the result with that obtained by
simulations, and discuss the mechanism of the competition of these two orders.
We also study how the supersolid region shrinks as the on-site repulsion
becomes strong.Comment: 6 pages, 6 figure
Development of measuring method for softness of epidermis using rotational step response
We have proposed a new measuring method for the softness of epidermis using rotational step response. It can be proceeded that horizontal torsional step is given periodically to the human skin surface by rotational step motor. Then dynamically epidermal characteristic is abstracted selectively from the human skin minimizing influence of the subcutaneous tissue. The cylindrical rotor is attached to the shaft of step motor and its external area is surrounded by the cylindrical guard ring; therefore, only human skin surface of inside the guard ring is screwed periodically by its rotor. At this moment, viscoelasticity of the epidermis is evaluated from analyzing the inducting coil of the step motor. The waveform of voltage of inducing coil can be characterized by overshoot P1, damping ratio D and undamped natural frequency ωn. The softness Ks that indicates viscoelasticity of the epidermis can be calculated from these parameters. Many experimental results showed that the softness Ks corresponds to the human sense and it is rational as a parameter for the human skin characteristics. This system is very useful as the measurement can be done easily, in vivo, and non-invasively. It also can be constructed simply without special mechanical sensor because step motor acts as not only driving but also sensing </p
- …